Reaction mass of [3-(trimethoxysilyl) propyl]urea, [3-(dimethoxyethoxysilyl) propyl]urea, [3-(methoxydiethoxysilyl) propyl]urea and [3-(triethoxysilyl) propyl]urea.

Endpoint summary

Description of key information

No studies are available. Based on molecular structure, molecular weight, water solubility, and octanol-water partition coefficient. It can be expected that the registered substance is likely to be absorbed via the oral and dermal routes, but not via inhalation. Hydrolysis occurs rapidly, and exposure is expected to both the parent substance and the hydrolysis products. Based on the water solubility, the registered substance and its silanol-containing hydrolysis product are likely to be distributed in the body, and excretion via the renal pathway can be expected. The bioaccumulation potential is expected to be low.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Additional information

There are no studies available in which the toxicokinetic properties of ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters have been investigated. Therefore, the toxicokinetic behaviour assessment of the substance and its hydrolysis products was estimated by its physico-chemical properties and the available toxicology studies on the substance itself.  

Ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters hydrolyses rapidly in contact with water (mean half-life less than 12 hours), generating methanol/ethanol and [3-(trihydroxysilyl)propyl]urea. This suggests that systemic exposure to both the parent and to the hydrolysis products is possible. Hence, this toxicokinetic behaviour assessment will try to predict the behaviour of these substances. The toxicokinetics of methanol/ethanol are discussed elsewhere and are not included in this summary. 

The molecular weight range of ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters is 222.1-264.4 g/mol. In contrast, the molecular weight of [3-(trihydroxysilyl)propyl]urea is 177 g/mol. The hydrolysis products are smaller in size and are more water soluble and, thereby suggest that they will have greater potential to be absorbed through biological membranes than the parent substance. Furthermore, the moderate range of log Kow of -0.2 to 1.3 for the parent substance and the log Kow of -3.3 for the hydrolysis product indicate that these substances may efficiently pass through biological membranes by passive diffusion or through the epithelial barrier by the bulk passage of water, respectively.

 

Absorption

Oral:

In an acute and a repeated-dose oral toxicity study with ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters no signs of systemic toxicity were observed, thus no prediction of systemic availability is possible. If ingestion occurs, the hydrolysis of the parent substance in the low pH of the stomach will be rapid, so any absorption of the parent substance is expected to be minimal and it is more likely to be the hydrolysis product that is absorbed.

The moderate range of log Kow of -0.2 to 1.3 for the parent substance and the log Kow of -3.3 for the hydrolysis product indicate that these substances are lipophilic enough to efficiently pass through biological membranes by passive diffusion or through the epithelial barrier by the bulk passage of water, respectively.

Inhalation:

The vapour pressure of the liquid parent substance (30.3-1.5 Pa) and the boiling point (>270°C) indicates that inhalation of the registered substance as a vapour is unlikely. 

Dermal:

The moderate log Kow (-0.2 to 1.3) and molecular weight (222.1-264.4 g/mol) of the parent substance suggest that absorption via the dermal route is possible. Slight induction of erythema by the test substance after dermal exposure could enhance dermal absorption.

Metabolism:

Ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters hydrolyses rapidly in contact with water (half-life <12 h), generating methanol/ethanol and [3-(trihydroxysilyl)propyl]urea. There are no data regarding the enzymatic metabolism of ureidopropylsilanetriol.

Excretion:

The low molecular weight and moderate water solubility of the parent and hydrolysis products suggest that they are likely to be excreted by the kidneys into urine.